The invention relates to an apparatus capable of delivering fluid. More specifically, the present invention relates to angiographic devices, or power syringes, for injecting contrast media, such as x-ray dye, or carbon dioxide into a patient at a mechanically controlled rate and pressure during angiography. The objective of the angiogram x-ray must be twofold: (1) do not injure the patient, and (2) create the best angiogram x-ray possible. Patient discomfort, too much contrast media or carbon dioxide being delivered to a patient, and over-pressurizing the arteries are some of the problems of present angiographic devices. It is believed that the present invention will achieve these objectives and overcome the disadvantages of other devices in the field of the invention, but its results or effects are still dependent upon the skill and training of the operator.
While the following concentrates on the delivery of contrast media to a patient during angiography, it is to be understood that carbon dioxide, or other suitable gas which requires high pressurization for delivery, may be delivered to a patient by the present invention.
Prior coronary angiography procedures involved using either a hand-held syringe or a syringe driven by an electrically powered injector; however, both of these devices have deficiencies. Use of hand held syringes is limited to small arteries which require 5-7 cc of contrast media and do not require high pressure delivery. Angiography of large vessels and vascular chambers (left atrium, left ventricle, aorta, cerebral vessels, renal arteries, upper extremity vessels, vena cavae, lower extremity vessels, right atrium, right ventricle and pulmonary arteries) require more pressure, and thus more physical power than an operator can reasonably and effectively supply to hand-held syringes.
While use of an electrically powered angiographic injector system overcomes this deficiency of the hand held syringe, it still has several disadvantages. The electrically powered injector system is a large, cumbersome system that involves using either a 65 cc or a 130 cc syringe. It is cumbersome to load and unload, resulting in consistent waste of expensive contrast media. The syringe is loaded into the power drive mechanism and is filled with contrast media by drawing the contrast media into the syringe by moving the driving mechanism backward, which draws the contrast media into the syringe. Once loaded with contrast media, air, along with any particulate material, must be cleared from the system. The syringe is de-aired by jogging the screw drive of the machine forward and then physically beating the machine with your hand or a rubber hammer. The machine is then set to various control parameters. The most important parameter is the pressure setting. The electrically powered injectors have pressure settings from 150 to 1,200 psi. Once the machine is engaged, the contrast media is delivered at approximately the pressure setting dialed in. The contrast media cannot be easily stopped once the machine begins to operate. Because of the inability to modify the pressure setting during delivery, severe patient discomfort can result. Patient discomfort, such as the intense hot flash which is experienced frequently during angiography, is directly related to the contrast media being injected into the patient at pressures higher than necessary. Also, the sudden blast of injection can cause the catheter to become displaced or cause cardiac arrhythmia or injury to the vascular cavity.
The injection pressure of contrast media not only affects the comfort level of the patient, it also affects the clarity of the angiogram x-ray. Excessive contrast media will create a bright spot on the x-ray. Insufficient contrast media will create a dark spot on the x-ray. Therefore, it is very important that the proper amount of contrast media, as well as the pressure and rate at which it is delivered, be controlled for safe, desirable results.
Other syringe injectors also have certain disadvantages. One syringe injector includes a syringe which is held in place by a frame and the plunger is attached to a connecting rod extending from the back of the plunger to a lever attached to the frame. While this design overcomes some of the deficiencies of hand-held syringes, it is not designed for injecting contrast media into the larger vessels in vascular chambers of the circulatory system. Specifically, it does not prevent contrast media from leaking out of the back of the syringe reservoir which can occur under high pressures. It also requires the operator to pull forward, then push downward thereby preventing the operator from applying steady pressure and effectively controlling the delivery of contrast media. These devices require the operator to pull the lever forward and, then, once the lever has been moved to an angle less than 90.degree. with the base, push down.
Accordingly, prior to the development of the present invention, there has been no apparatus for delivering fluid to a patient which: allows the operator to maintain control of the rate and pressure of delivery of the fluid, such as contrast media; assists in creating clear angiogram x-rays; and reduces patient discomfort. Therefore, the art has sought an apparatus for delivering fluid to a patient which: allows the operator to maintain control of the rate and pressure of delivery of the fluid, such as contrast media; assists in the creation of clear angiogram x-rays; and reduces patient discomfort.